(1.) Field of the Invention
The present invention relates to a shuttle type line printer comprising a shuttle making a reciprocating movement along the direction of the printing line, printing hammers arranged equidistantly on the shuttle and printing pins arranged on the free ends of the printing hammers to effect the printing operation.
(2.) Description of the Prior Art
In a conventional shuttle type line printer, to a rectangular shuttle making a reciprocating movement along the direction of the printing line is fixed a first yoke having a size similar to the size of the shuttle, and a rectangular permanent magnet having a length similar to that of the first yoke is secured to the upper portion of the first yoke and a second yoke having a size similar to that of the first yoke is secured to the upper portion of the permanent magnet. A plurality of projections are equidistantly formed on the second yoke on the side of printing paper, and coils are wound on the respective projections to form a plurality of electromagnets. A plurality of printing hammers are arranged equidistantly in the direction of the printing line on the first yoke on the side of printing paper so that the number of the printing hammers is equal to the number of the electromagnet and the distance between every two adjacent printing hammers is the same as the distance between every two adjacent electromagnets. Printing wires for urging these printing hammers are secured to the printing paper sides of the free ends of the respective printing hammers. Accordingly, a magnetic path defined by the permanent magnets, yokes, electromagnets and printing hammers constituting printing elements of the line printer is formed on the rectangular shuttle.
One end in the longitudinal direction of the shuttle is connected to an eccentric cam for reciprocating the shuttle along the direction of the printing line. Namely, the shuttle is reciprocated along the direction of the printing line by rotation of the eccentric cam. At this reciprocating movement, the force of inertia is generated in the longitudinal direction of the shuttle, that is, on the left side or right side of the shuttle due to the mass of the shuttle. This force of inertia is considerably large because the shuttle is formed of by a large-size permanent magnet having a large mass and yokes. Accordingly, the shuttle type line printer severely shakes from left to right. In the conventional shuttle type line printer, in order to prevent this shaking, a balancer having a mass equal to or similar to the mass of the shuttle is attached along the shuttle, and this balancer is reciprocated in the opposite direction to the direction of the reciprocating movement of the shuttle by means of an eccentric cam. If this arrangement is adopted, the force of inertia generated by the reciprocative movement of the shuttle is cancelled or reduced by the reverse force of inertia generated by the reciprocal movement of the balancer, whereby shaking of the shuttle type line printer is diminished.
Since the shuttle bears a large-size permanent magnet, yokes and the like, the weight of the shuttle is considerably heavy, and therefore, a balancer having a large size and heavy weight should be used and in some cases, the size and weight of the printing zone of the shuttle type line printer are substantially occupied by those of the shuttle and balancer. Namely, the size and weight of the printing zone are about 2 times the size and weight inherently necessary for the printing zone.
Accordingly, in the conventional shuttle type line printer, the size and weight are increased by the balancer, and therefore, it is very difficult to increase the speed of operation. Moreover, even if high speed operation is possible, since not only the shuttle but also the balancer having a mass similar to that of the shuttle should be driven, the energy consumption is increased, and a desire to provide a small -size, high-speed printer having a reduced energy consumption is not realized. Furthermore, since additional materials and parts are necessary for the balancer, the manufacturing cost is increased. It may be said that development of shuttle type line printers is inhibited by the above-mentioned defects.